1. Field of Invention
This invention relates to improved inverted tooth chain especially adapted for automotive use, such as for timing chains; the chain, however is adaptable for other power transmission applications.
2. Background Discussion
Inverted tooth chains are well known in the art and many are especially adaptable for automotive use, such as for timing chains. Many timing chains are of the roller chain construction, as well known in the art. These chains mesh wit sprockets with their rollers drivingly engaging the flanks of the sprocket teeth. Other chains for the same purpose are of the "silent" or inverted tooth variety, comprising a plurality of interleaved sets of links, each set of links being joined to the next adjacent set of links by a pivot means, such, for example, a round pin or a multiple piece rocker joint. The various types of pivot means are well known in the chain art and need no further description.
The links of silent or inverted tooth chain are constructed with a body having a pair of spaced openings to receive the pivot means, and a pair of depending toes separated by a crotch. The toes are defined by diverging inside and outside flanks, the flanks usually drivingly contacting the teeth of the sprockets in the drive in which the chain is used. Guide links flanking the outsides of the links of the chain or located centrally thereof serve to maintain meshing engagement of the chain with the sprockets. The guide links are placed are shaped to avoid any driving contact with the sprocket teeth. In any event, the pitch of all links is the same.
Customarily, the links of a chain are stamped or blanked at relatively high rates of speed from metal strip and later treated to insure the proper hardness of the links. The pivot means can be cord wood cut from an extruded metal shape and then hardened to improve the wearing characteristics of the part and thus the finished chain. The chain is assembled in a continuous length with specific lengths being "broken" out, and the ends of each length being joined to complete the loop. Various methods are used to maintain the sets of links in the assembled chain, as for example upsetting or peening over of a joint members at their ends, such methods being well known in the chain art.
When the links are customarily blanked, they are literally sheared from the strip material and the openings therethrough which receive the joint means, are likewise produced by the shearing action, resulting in an openings with walls that have a rough surface. Relative rotation between a joint member and such an opening causes the pin to rapidly wear, thus reducing the life of the chain.